February 6, 1999
By P. Weiss
A long-sought new element has apparently sprung into existence in a Russian laboratory. Heavier than any previously known element, it crams an unprecedented 114 protons into its nucleus. The real excitement, however, say nuclear physicists and chemists, is that it lasted 30 seconds before breaking down into lighter elements.
Bucking the trend toward briefer lives for increasingly heavy nuclei, the new element lasts 100,000 times longer than number 112, the last new element found (SN: 3/2/96, p. 134). The creators of element 114 believe they have finally set foot on the so-called island of stability, a postulated region of atomic properties populated by extraordinarily long-lived superheavy nuclei.
"Sure, they've found a new element and that's important, but what's really important is the island," says Albert Ghiorso of Lawrence Berkeley (Calif.) National Laboratory (LBNL).
For 30 years, theorists have predicted the existence of this islanda kind of Shangri-La where exotic elements stick around long enough to allow exhaustive studies of their nuclear behavior and chemistry. Researchers anticipate that the elements may display unusual properties.
Scientists from the Joint Institute for Nuclear Research in Dubna near Moscow and Lawrence Livermore (Calif.) National Laboratory collaborated to create the new element. In a prolonged experiment that produced just a single atom, the Russian scientists bombarded a film of plutonium-244, supplied by Livermore, with a beam of calcium-48 atoms for 40 days, says Dubna's Yuri Ts. Oganessian. They completed the work at the end of December 1998. A report of the find appeared Jan. 19 on Science's online news service.
The atom signaled its presence by disintegrating into lighter and lighter elements, from atomic number 112 to 110 to 108 and so on. Livermore's Kent Moody says his team's data analysis, completed Monday, identifies element 114 "to greater than a 99 percent probability."
Although the claim has yet to undergo peer review for publication, it's being well received in the heavy-element field. "The more we hear, the better it sounds," says Kenneth E. Gregorich, head of a LBNL team gearing up to rejoin the superheavy-element hunt next fall.
During more than a half-century of making increasingly proton-laden nuclei, scientists have found that such nuclei generally decay sooner than lighter ones. Repulsions between the many positively charged protons shatter the nucleus.
However, nuclei also contain uncharged neutrons, which can arrange themselves among the protons to make nuclei more durable than would otherwise be expected. Theorists have long suspected that element 114 would show remarkable nuclear stability.
Oganessian says he is confident that he and his colleagues have reached the shore of the long-sought island. Not only did the purported 114 atom last a long time, but certain isotopes in the decay chain, which also had never been seen before, had extraordinary life spans. For instance, isotopes of elements 112 and 108 in the decay chain lasted 15 minutes and 17 minutes, respectively, before disintegrating. Isotopes of an element have its allotted number of protons but varying numbers of neutrons.
The difficulty of identifying these novel decay products makes it hard to prove unequivocally that element 114 was created, says Sigurd Hofmann of GSI, the German center for heavy-ion research in Darmstadt. Further experiments at GSI, Dubna, and elsewhereincluding perhaps a repeat of the recent Dubna experimentshould help settle any doubts about the 114 claim, he says.
With a beachhead on the island established, Oganessian calls for forays inland. "We have to go now for more heavy isotopes," such as 116, he says.
From Science News, Vol. 155, No. 6, February 6, 1999, p. 85. Copyright © 1999, Science Service.
Copyright © 1999 Science Service